The invention relates to the distribution of services in a telecommunications network and the arrangement of control relationships for service programs.
The rapid development of the telecommunication field has made it possible for operators to provide users with services of many different types. One such network architecture providing advanced services is called the Intelligent Network, for which the abbreviation IN is generally used. Examples of such services are the Virtual Private Network VPN, which allows the use of short numbers between subscribers of the private network, and the Personal Number, where the intelligent network re-routes calls made to the personal number in a manner controlled by the subscriber. IN-services are utilized by various networks, such as mobile communications networks and fixed networks connected to IN.
The physical architecture of the intelligent network is illustrated in FIG. 1, where the physical entities are shown as rectangles or cylinders and the functional entities located in them are shown as ovals. This architecture is described briefly below, since references will be made to an intelligent network environment in the description of the invention to follow. An interested reader may acquire a more detailed understanding of the intelligent network from ITU-T recommendations Q.121X or from Bellcore""s AIN recommendations, for example. ETS 300 374-1 CorelNAP terms will be used in the description of the invention and of its background, but the invention can also be used in intelligent networks implemented in accordance with other intelligent network standards.
The Subscriber Equipment SE, which may be a telephone, a mobile station, a computer, or a fax, for example, is either connected directly to a Service Switching Point SSP or to a Network Access Point NAP. A service switching point SSP provides the user with access to the network and attends to all necessary dialing functions. The SSP is also able to detect the need for an intelligent network service request. In functional terms, the SSP includes call management, routing, and service dialing functions. In mobile communications networks, the mobile services switching center MSC can perform tasks which are performed by the SSP.
The Service Control Point SCP includes Service Logic Programs SLP, which are used to produce intelligent network services. In the following, xe2x80x9cservice programxe2x80x9d will also be used as a shorter form for xe2x80x9cservice logic programsxe2x80x9d.
The Service Data Point SDP is a database containing such data about the subscriber and the intelligent network which the SCP service programs use for producing individualized services. The SCP may use SDP services directly by way of a signaling or data network.
The Intelligent Peripheral IP provides special functions, such as announcements, and voice and multiple dialing identification.
The signaling network shown in the figure is a network according to Signalling System Number 7 (SS7), a known signaling system described in the Specifications of Signalling System No. 7 of the CCITT (nowadays ITU-T), Melbourne 1988.
The Call Control Agent Function (CCAF) ensures that the end user (subscriber) has access to the network. Access to IN-services is implemented through additions made to existing digital exchanges. This is done by using the Basic Call State Model BCSM, which describes the various stages of call handling and includes those points or Detection Points DP where the call handling can be interrupted in order to start intelligent network services. At these detection points, the service logic entities of the intelligent network may be in an interaction relation with the basic call and connection management function. In the exchange, the call set-up is divided into two parts: the call set-up in the originating half and the call set-up in the terminating half. As a rough description, call handling in the originating half is related to the services of the calling subscriber, while call handling in the terminating half is related to the services of the called subscriber. The corresponding state models are the Originating Basic Call State Model (O-BCSM) and the Terminating Basic Call State Model (T-BCSM). The BCSM is a high-level state automaton description of those Call Control Functions (CCF) needed for setting up and maintaining a connection between the users. Functionality is added to this state model with the aid of the Service Switching Function (SSF) (cf. partial overlapping of CCFs and SSFs in FIG. 1) to make it possible to decide when intelligent network services (i.e., IN-services) should be requested. When IN-services have been requested, the Service Control Function (SCF), including the service logic of the intelligent network, attends to the service-related processing (in call establishment). Thus, the Service Switching Function SSF connects the Call Control Function CCF to the Service Control Function SCF and allows the Service Control Function SCF to control the Call Control Function CCF.
The intelligent network service is implemented in such a way that in connection with the encounter of service-related detection points the Service Switching Point SSP asks the Service Control Point SCP for instructions with the aid of messages relayed over the SSP/SCP interface. In intelligent network terminology these messages are called operations. The SCF may request, for example, that the SSF/CCF perform certain call or connection functions, such as charging or routing actions. The SCF may also send requests to the Service Data Function (SDF), which provides access to service-related data and network data of the intelligent network. Thus the SCF may request, for example, that the SDF fetches data concerning a certain service or that it updates this data.
The above functions involved in interaction with the subscriber are supplemented by a Specialised Resources Function SRF providing an interface for those network mechanisms. Examples are messages to the subscriber and the collection of the subscriber""s dialing.
The following is a brief description of the role of the functional entities shown in FIG. 1 in terms of IN-services. The CCAF receives the service request made by the calling party, which is typically made by the calling party lifting the receiver and/or dialing a certain number series. The CCAF relays the service request further to the CCF/SSF for processing. The CCF has no service data, but it is programmed to identify those detection points where a SCP visit might be made. The CCF interrupts the call set-up for a moment and gives the service switching function SSF data about the detection point encountered (about the stage of call set-up). It is the duty of the SSF through use of predetermined criteria to interpret whether the task is a service request related to intelligent network services. If this is the case, the SSF sends to the SCF a standardized IN-service request, including data related to the call. The SCF receives the request and decodes it. Then it works together with the SSF/CCF, SRF, and SDF in order to produce the requested service for the end user.
As was presented above, service is started when the SSF sends to the SCF a standard IN-service request. The service request may be sent during certain stages of the call. FIG. 2 illustrates a few basic operations of a state-of-the-art function of an intelligent network at detection points. At point 21 the SSP sends to the SCP an InitialDP service request, including basic data on the call for starting the intelligent network service. Thereupon the arming of detection points in the SSP follows. At point 22 the SCP sends to the SSP a RequestReportBCSMEvent operation telling the SSP which detection points it should report to the SCP. Next, at point 23, the SCP typically sends charging and/or interaction operations, such as ApplyCharging (e.g. a request for a charging report) or PlayAnnouncement (give an announcement to the subscriber). At point 24 the SCP sends to the SSP a routing instruction, such as Connect (route the call to a new number) or Continue (continue the call set-up with the same data). When it meets the detection point reserved by the SCP, the SSP sends to the SCP an EventReportBCSM operation at point 26.
Detection points determined in intelligent network architecture are the primary mechanism for reporting various events. The events 21-24 in FIG. 2 described above relate to a detection point called the Trigger Detection Point (TDP). The SSP may make an initial inquiry concerning a service to the SCP in connection with a TDP detection point, and the SSP then receives instructions for call handling. Another type of detection point is called the Event Detection Point (EDP). Point 26 in FIG. 2 shows a moment when in the course of a call an EDP detection point is encountered. The SSP reports on the encounter with the detection point to the SCP, which at point 28 sends additional call instructions to it. The Event Detection Point Request required (EDP-R) is a detection point after the encounter of which the processing of the call at the detection point will stop until the SCP sends additional instructions. Arming of the EDP-R detection points creates a control relationship between the SSP and a particular service program of the SCP. A control relationship means that a session is going on between the call set-up half and the SCF, and during this session the SCF may give instructions to change the handling of the call. In a monitoring relationship the SCP is not able to affect the progress of the call handling; it can only ask the SSP to report on various events related to the call. In accordance with the current intelligent network standard, there can be only one control relationship but several monitoring relationships related to a call. Thus a problem with EDP-R detection points is that they prevent the production of any additional services. This is especially problematic when one service program reserves a control relationship for the whole duration of the call by arming a detection point to be met at the end of the call as an EDP-R detection point, whereby no more intelligent network services can be started during the call in question. The operation of an intelligent network is thus based on the fact that only one service program (SCP relationship) at a time can have a control relationship and can thus control the SSP. This principle is commonly referred to as a single point of control.
For capacity purposes and so on, it is advantageous to distribute the tasks of intelligent network services logically, e.g. according to their type of task, into separate service programs in one or several SCPs. The same applies for service packets used in other telecommunications networks, such as in mobile communications networks. Patent application publication GB-2315639 presents a method for implementing the control of a distributed service in IN. When the first control point SCP1 detects that at least a part of the service should be processed at another control point SCP2, SCP1 sends to the service switching point SSP a message, with precise instructions to send a service request to SCP2. This instruction includes the network address for the other control point SCP2 to which the control should be transferred. When the SSP sends the service request to SCP2, the connection between the SSP and SCP1 ends and a new connection is set up between the SSP and SCP2. The method according to the publication requires that each SCP knows the services of the other control points and is thus able to direct the service request of the SSP to the correct address. Availability of this data is thus a problem, with the solution according to the publication, especially in joint use of control points by different service providers. In addition, it is a problem with prior art solutions that only one service program at a time can give instructions to the switching point.
It is the purpose of this invention to make possible a flexible distribution of service programs in a telecommunications network, as well as the versatile simultaneous use of the service programs.
These purposes are achieved through a method and a switching point according to the invention which are characterized by the independent claims. Different embodiments of the invention are presented in the dependent claims.
The invention is based on the idea that the controllability of a connection is divided into parts by grading different degrees of controllability, so-called controllability classes, within each of which there is preferably a single point of control. The controllability class defines a certain set of such instructions provided by the service program which are acceptable to the switching point in this controllability class. The controllability of connections is thus based on sub-functionality. Simultaneous controllability of several service programs is thus made possible, that is, permission to provide the switching point with call handling instructions can be given to several service programs to be carried out simultaneously, provided that the instructions belong to different controllability classes. Service programs pertaining to different controllability classes can thus simultaneously control the operation of the switching point through means determined by their respective controllability class. Available controllability classes are allocated to service programs according to the controllability requirement of said programs. The division of controllability is within the state model (O-BCSM or T-BCSM). The allocation of a controllability class in one BCSM of the call may also affect other BCSMs of the call, e.g. prevent services requiring the same controllability class from starting.
Distribution of the control of the switching point has the advantage that it makes possible the versatile starting of intelligent network services. The switching point can be controlled simultaneously by several service programs of different controllability classes as a multi-point of control.
Another advantage of service distribution according to the invention is that it makes possible diversified service combinations.
A further advantage of the method according to the invention is that service programs can be distributed more freely without adversely affecting functionality.